Profoundly deaf children whose lives could be transformed by ear implants are failing to reap the benefits, say experts.

A study published in the Lancet medical journal has highlighted the potential gains which could be achieved.

Completely deaf children were, on average, able to identify almost 45 words a minute after five years using the implants.

The earlier the child is identified and assessed the better

Dr Kaukab Rajput, Great Ormond Street Hospital

However, despite a willingness by health authorities to fund the £17,000 implants, but many children are not being diagnosed early enough.

It takes years for the child to learn the skills to combine the "sounds" perceived through the implants with conventional lip-reading.

Unless the implant is put in place well before he or she reaches school age, key development time is lost.

Dr Kaukab Rajput, a consultant audiological physician at the cochlear implant department at Great Ormond Street Hospital in London, stressed the importance for parents to be vigilant for early signs of hearing problems in their children so that diagnosis could be made as early as possible.

She said: "The earlier the child is identified and assessed the better.

"The age at which the implant is put in is very important."

A spokesman for the Royal National Institute for Deaf People said: "Children are definitely missing out, not just on cochlear implants, but on a whole range of options.

"Language acquisition is crucial in any child - when that child can't hear, it becomes even more crucial that different methods of communication are started as early as possible."

Traditional aids fail

A cochlear implant is only used when traditional hearing aids are of absolutely no benefit to the child.

It uses a microphone to pick up sounds, which are then passed to a speech processor, which is worn on the body like a Walkman.

This converts the speech into electronic signals which are then transmitted to a receiver implant implanted behind the ear.

A wire from this passes the signal into the inner ear and the cochlear nerve which carries it to the brain.

Patients suitable for cochlear implantation are often those rendered completely deaf by a genetic defect, although meningitis at a very young age was another reason for deafness.

Only a percentage of profoundly deaf children are suitable for the operation.

The government has recently announced that all newborn children will receive a hearing test before they leave hospital.